：设计了一种PMMA自由曲面透镜，用于无导光板结构的LED平板灯。该透镜基于自由曲面透镜的折射和全反射原理实现出射光的重新分布，可用于均匀照明LED平板灯的出光面板。采用数字仿真和实验制作进行设计。仿真结果表明，当自由曲面透镜与出光面板的距离为5 mm、自由曲面透镜旋转为0°、LED与自由曲面透镜的距离为7 mm时，LED平板灯出光效率较高且整灯均匀性达96.6%。实验结果表明，所设计的自由曲面透镜可使无导光板结构的LED平板灯的面板均匀性达95.74%，与数字仿真近似相等。

A design of the freeform lens made by PMMA for the LED flat light applications was presented. This lens can be used to achieve the uniform illumination of the flat target of the LED flat light, which is based on the principle of freeform surface of the refraction and total reflection principle which realize redistributing the out light. A numerical method and experimental method were used in the design. The simulation results show that when the distance between the freeform lens and the flat target is 5 mm, rotation angle is 0°, the distance of the freeform lens and the LED is 7 mm, the uniformity of the whole lamp is up to 96.6% with the high luminous efficiency. The experimental results show that under the action of freeform lens, the uniformity of the flat target of the LED flat light without the guide plate is 95.74%, which is similarly equal to the digital simulation.